No I actually want the letterbox look on the DV clip, so this mean I would have to scale that ??
If your dv clip is 4:3 and you want letterbox you have to put black bars over the clip.
In that case you loose top and bottom of that clip.
You can make them yourself in the titler or there is a ready made template in the titler.
I'm thinking more about the 16:9 part, and that got me thinking... (Ann, where am I going wrong?)
Why use a 4:3 sequence? And what will you really have if you burn in letter boxing in a 720x480 sequence? For most 4:3 exports, the DVD player/TV combo will add the letterboxing, and th4e problem is how to handle the HDV clip in a 4:3 sequence.
I think your original picture is wrong. You should use an HDV sequence (so 16:9), and don't scale the DV, so it will be pillar boxed.
If you watch this on a 4:3 TV, you will see it letterboxed (because the overall frame is 16:9), but the 4:3 section will also be pillarboxed. To get the 4:3 section to "match" the 16:9 (without stretching it), you would have to scale it up and crop the top and bottom.
If you watch this on a 16:9 TV, it will fill the screen, and the 4:3 section will be pillarboxed. As before, to get the 4:3 section to "match" the 16:9 (without stretching it), you would have to scale it up and crop the top and bottom.
Why use a 4:3 sequence?
Because if you put 4:3 material into a 16:9 sequence, you will have to scale it up to fill side to side. And that's generally bad advice. Upscaling causes degradation.